1. Field of the Invention
This invention relates to sludge collectors for removing sludge from rectangular settling tanks and more particularly to a wear strip assembly for supporting a flight for use in sludge collection.
2. Description of Related Art
Sludge collectors are commonly used in waste water treatment plants to scrape settled sludge from the bottom of the settling tank and also to skim floating waste off the surface of the waste water. These sludge collectors typically include a number of sludge flights which are usually elongated members that extend the width of the tank. The ends of the flights are connected to drive chains which carry flights in a circuit lengthwise along the bottom of the tank and back over the surface of the water to perform the scraping and skimming functions.
Rectangular settling tanks used in waste water treatment facilities typically include field installed steel T-rails having floor wear bars disposed on the T-rails for supporting the flight when collecting sludge. The T-rails may be spliced together with separate steel plate splice bars and may be secured to the concrete floors of the settling tank by the use of standard hardware. Alternatively, the floors of the settling tank may be poured without T-rails and the wear bars may be directly mounted to the concrete floors.
Because wear bars are often formed of non-metallic material, such as UHMW polyethylene, nylon, or polyurethane, they have a different coefficient of linear expansion than the concrete floors or steel T-rails to which they may be mounted and special design considerations must be made. Wide variances in the ambient temperature within the concrete basins during installation or variances in water temperature when in final operation are common and therefore the wear bars may become loose, buckled, or otherwise out of line. Consequently, the flights may become jammed and may result in breakage of the chain supporting the flights.
Further, because wear bars are typically secured to the T-rail or concrete floor by screws or bolts, a portion of the wear bar surface is lessened due to the presence of these fasteners. Moreover, a multitude of fasteners may be needed to secure the wear bars to the concrete floors or T-rails, adding to the overall cost and field labor required. It is therefore desirable to have a wear bar that may be secured to the bottom of a settling tank without the use of screws or bolts so that the total wear bar surface may be utilized and the installation is less costly, easier to install and easier to replace when necessary.